The need for methods of assessing the impact of environmental pollutants on ecological systems has led to the development of procedures which utilize living organisms as biological monitors. The simplest and most convenient of these systems utilize unicellular microorganisms, since they are most easily maintained and manipulated.
Unicellular organisms, however, are inadequate models for estimating the potential effects of pollutants on complex multicellular animals, as they do not have the ability to carry out biotransformations. Biotransformations of chemical compounds by multicellular organisms is a significant factor in determining the overall toxicity of agents to which they are exposed. This fact has stimulated the search for model organisms in the latter category which could serve as biomonitors. The nematode, Caenorhabditis elegans, has become a widely used model system for genetic and molecular biological studies, and the ease of culture and handling of this organism has lead to the proposed use of this and related species as biomonitors in various applications. Some examples from the recent literature are:
1. Williams, P. L. and Dusenbery, D. B. "Using the nematode Caenorhabditis elegans to predict mammalian acute lethality to metallic salts." Toxicol. Ind. Health 4(4), 469-478, 1989. PA1 2. Williams, P. L. and Dusenberry, D. B. "A promising indicator of neurobehavioral toxicity using the nematode Caenorhabditis elegans and computer tracking". Toxicol. Ind. Health 6(3-4), 425-440, 1990. PA1 3. Williams, P. L. and Dusenbery, D. B. "Aquatic toxicity testing using the nematode, Caenorhabditis elegans". Environ. Toxicol. Chem. 9, 1285-1290, 1990. PA1 4. Samoiloff, M., "The nematode toxicity assay using Panagrellus redivivus". Toxic. Assess. 5(3), 309-318, 1990. PA1 5. Van Kessel, W. H. M., Brocades Zaslberg, R. W. and Seinen, W. "Testing environmental pollutants on soil organisms, using cadmium chloride and nematodes". Ecotoxicol. Environ. Saf. 18 (2), 181-190, 1989.
Over the last 15 years or so, it has been established that all organisms respond to heat stress and to a variety of chemical stresses by producing specific proteins which are made either at much lower levels or not at all under normal conditions. This realization has led to proposals for monitoring the environment by measuring the levels of these proteins in various organisms (1,2,3). These approaches involve extraction of the proteins and measurement of their levels, usually using antibodies.
The invention described herein utilizes a different approach, i.e, we have linked the control regions which regulate stress protein production to a gene which produces a readily measurable enzyme (a "reporter gene"). This reporter gene has been inserted into the chromosomes of C. elegans to produce transgenic strains which respond to stress by making the reporter enzyme. To complete the biomonitor system, methods have been designed for rapidly and conveniently assessing the magnitude of the reporter enzyme activity, as well as its tissue location in the nematode. The recombinant strains, together with the assay methodology, can constitute a biomonitoring "kit" which can be used to detect the level of stress imposed on an organism by exposure to water samples (salt or fresh water), sludges, sediments, soils, soil extracts, pesticides, etc.